Device for controlling the temperature and protecting against excessive flow of current of electric installations

Abstract

A device for controlling the temperature and protecting against excessive flow of current of electric installations, said device being provided with a mechanical switch which opens itself at a definite previously selected temperature, said mechanical switch comprising cylindrical housing wherein two elastic contact means are provided, one of the contact means comprising an open spring spiral torsion with bent ends which is provided around a melting body of thermally softenable material and is pressed with a tension directly against the spring action of the other contact means.

I claim: 
     
       1. A thermal cut-off switching device for connection in series with an electrical component or appliance which is liable to failure from overheating if the energizing current continues without interruption above a known temperature, said device comprising a shaped cylindrical fusible element,   a circular spring evenly gripping said shaped cylindrical fusible element,   a miniature cylindrical housing of insulation material containing said fusible element and said circular spring, with an end cap fitted to said housing anchoring one end of said circular spring in a floating anchorage,   a cantilever spring detained by said circular spring in balanced electrical contact,   said cantilever spring being anchored at its fulcrum by fitting into a slot formed by said housing   said electrical contact between said two springs being balanced into parallel surface contiguity by at least one of said springs having a floating anchorage,   said balanced electrical contact being maintained on a surface of the cantilever spring by an extremity of the circular spring,   said electrical contact adapted for termination by the removal of the extremity of said circular spring from contact with the surface of said cantilever spring, the instantaneity of contact breakage being decided by the mechanical termination of said cantilever spring and the resultant acceleration of said cantilever spring about its fulcrum to its tempered position,   said removal of the extremity of said circular spring being caused by the collapse of said fusible element at a predetermined temperature thus permitting said circular spring to coil up on itself in the direction of its other anchored extremity, any slow or creeping movement preceding the collapse of said fusible element not being transmitted to the actual separation of the two contacts, this separation being decided solely by the mechanical construction,   this separation of the ends of said two springs being accelerated after the release point by the summation of accelerations in opposite directions caused by the moments of both said springs acting in complex functions of arc, said acceleration reducing the formation of flame, welding and arc when an electric current is broken.   
     
     
       2. A device according to claim 1, further characterized by said circular spring being a spiral torsion spring having a bent end,   said torsion spring detaining said cantilever spring by said bent end acting as a deteret on the upper side of said cantilever spring.   
     
     
       3. A device according to claim 1, further characterized by said circular spring being a spring ring having a bent end,   said spring ring detaining said cantilever spring by said bent end from the upper side of said cantilever spring.   
     
     
       4. A device according to claim 1, further characterized by said circular spring having a bent end,   said circular spring detaining said cantilever spring by said bent end from the lower side of said cantilever spring.   
     
     
       5. A device according to claim 1, further characterized by said fusible element being of a thermally slow softening material.   
     
     
       6. A device according to claim 1, further characterized by said cylindrical housing having an oblong slot through which an end of said circular spring extends and which fixes said end.   
     
     
       7. A device according to claim 1, further characterized by said cylindrical housing having a slot in its upper side, said slot having an upper width narrower than the width of said cantilever spring which extends therethrough.   
     
     
       8. A device according to claim 1, further characterized by said cylindrical housing having an inner profile shaped to support said circular spring and to receive said cantilever spring pressed thereagainst.   
     
     
       9. A device according to claim 1, further characterized by a thermistor with a positive temperature coefficient connected in series with said springs.